Watch Avalanche Video

An avalanche is a rapid flow of snow down a sloping surface. Avalanches are typically triggered in a starting zone from a mechanical failure in the snowpack when the forces on the snow exceed its strength but sometimes only with gradually widening. After initiation, avalanches usually accelerate... Show More

An avalanche is a rapid flow of snow down a sloping surface. Avalanches are typically triggered in a starting zone from a mechanical failure in the snowpack when the forces on the snow exceed its strength but sometimes only with gradually widening. After initiation, avalanches usually accelerate rapidly and grow in mass and volume as they entrain more snow. If the avalanche moves fast enough some of the snow may mix with the air forming a powder snow avalanche, which is a type of gravity current. Slides of rocks or debris, behaving in a similar way to snow, are also referred to as avalanches. The remainder of this article refers to snow avalanches. The load on the snowpack may be only due to gravity, in which case failure may result either from weakening in the snowpack or increased load due to precipitation. Avalanches that occur in this way are known as spontaneous avalanches. Avalanches can also be triggered by other loads such as skiers, snowmobilers, animals or explosives. Seismic activity may also trigger the failure in the snowpack and avalanches. Show Less